I’ve done some more testing and data collection. I plan to continue doing more including some beam shot stuff since that seems to be a thing. I’ll post it here as I go.
For starters, the light’s internal charge circuit results in a battery with 4.14V after resting disconnected for about 15 minutes.
When charging another device, the flashlight will stop charging when it reaches what it thinks is 25% remaining on its own battery. I seem to consistently get about 40% charge of a LG V20 phone with the phone in-use during charge and the flashlight used as a flashlight for a few hours on low prior to charging the phone. More consistent testing here is required but I like these results so far since I can just use the flashlight as a flashlight but still get a good chunk of life for my phone (or wife’s phone) at any time. Since I now know the cutoff for charging is 25% I’m going to use it as a light until it reaches 50% indicated, sample the battery voltage, then charge the phone.
Any other suggestions for testing would be much appreciated! I recently picked up a Lumintop Tool AA 2.0 for those eventual beam shots since that seems to be a very popular light. I realize it is nowhere near the top output rating of the XR2 but it will be something to compare that is recent and common.